People

Converting Sunlight to
Electricity

by Clare Coppa

In Vision 21 [Nov. 8], Time magazine projects, “Rooftop solar panels will supply electricity to our appliances and to a basement fuel cell, which will produce hydrogen. When the sun is not shining, the cell will operate in reverse, using the hydrogen to make electricity.”

Shortening the path to home-produced electricity, George Kelly, a member of ASTM Committee E-44 on Solar, Geothermal and Other Alternative Energy Sources, has worked in the solar industry nearly two decades. His latest project is an array of photovoltaic (PV) modules that converts sunlight to electricity which he installed in 1998 on the roof of his home in Mt. Airy, Md. A home weather station and a data acquisition system compare the amount of sunlight available to the amount of power produced. “It’s kind of a hobby in that I like doing all the wiring and fiddling around with the gadgets,” says Kelly.

Does Kelly’s system power his all-electric 1600 sq. ft. (150 sq. meter) home and completely run appliances for Kelly’s family of four? No, but it’s a step toward future all-solar homes. “The cost of fossil fuels will continue to rise, the cost of solar is going to continue to fall, and as people use more solar, the price will drop even further and then it will really take off,” he predicts. “In the last maybe four to five years, there has been a big emphasis on grid-connected applications for residential or commercial rooftops.”

Kelly helped to develop the easy-to-install interlocking PV modules on his roof with BP Solarex, a manufacturer of solar products in Frederick, Md., and his employer of 19 years. Eight PV modules “with no moving parts and nothing to wear out” feed direct current (DC) into a small electric box on the side of the house which connects a cable to a basement inverter that converts the DC to about 60 kilowatt hours of AC (alternating current) monthly.

“The point of the residential roof market,” says Kelly, “is just the available area. There are millions of houses in the U.S. with hundreds and thousands of square miles of roof area. If you covered all of it with solar modules, instead of just sitting there, it could be producing power to be fed into the electric grid. Instead of needing new power plants, either coal, hydroelectric, or whatever, you could use all of the empty roof top space to generate electricity.”

Progressing swiftly, Kelly added a ninth module which he also helped to develop that eliminates the need for an inverter in the basement. An inverter on the back of the module converts sunlight into AC electricity on the roof and feeds the house current.

“Anything that runs off of electricity can be run with PV modules,” he explains. “Especially in places where it’s sunny most of the year, like Phoenix, or southern California. In some remote areas where it would be very expensive to bring in a power line, it is more cost effective to install solar modules. There are already completely solar-powered homes that are independent of the local utility grid.”

Solar research boomed after the 1970s oil crisis with funding from the Carter administration. Kelly entered the field in 1980 after attaining a B.S. in architecture from Catholic University, Washington, D.C. Shortly after graduation, he joined BP Solarex and helped to produce PV solar modules that fueled NASA missions. “Probably the most famous one that we worked on was the Magellan, which went to Venus, orbited it, and made maps,” he recalls.

With members of ASTM Subcommittee E44.09 on Photovoltaic Electric Power Conversion, Kelly wrote Standard E 2047, Test Method for Wet Insulation Integrity Testing of Photovoltaic Arrays.

“It’s been the hope all along for the PV industry that oil prices were going to get really high and fossil fuels were going to run out so that people would have to use solar, wind, or other alternate energy. It hasn’t really happened that way. If you asked somebody in 1979 when the oil would run out they would have said 10 or 15 years. Well here we are 20 years later and there is still a lot of oil around and the prices haven’t shot through the roof and it hasn’t disappeared the way people thought. But, sooner or later it will.” //